POS1567 OUTCOMES AND PREDICTORS OF CHRONIC IMMUNE CHECKPOINT INHIBITOR INDUCED INFLAMMATORY ARTHRITIS: DATA FROM THE CANADIAN RESEARCH GROUP OF RHEUMATOLOGY IN IMMUNO-ONCOLOGY (CANRIO) RETROSPECTIVE COHORT
Authors: A. Ladouceur, L. Gonzalez Arreola, S. Jamal, M. Hudson, J. Pope, S. Hoa, J. Roberts, D. Moon, A. Karmali, T. Nevskaya, E. Schmidt, N. Toban, L. Cho, T. Barnetche, C. Ye
Journal: Annals of the Rheumatic Diseases (2023)

<h3>Background</h3> Immune checkpoint inhibitors (ICI) improve overall survival and progression-free survival in many types of malignancies and are the new pillar of cancer treatment <sup>[1]</sup>. ICIs harness a patient's own immune system to fight their cancer. However, this activation of the immune system can result in off-target immune-related adverse events (irAEs). One of the most disabling irAE is inflammatory arthritis (ir-IA) <sup>[2]</sup> affecting up to 7.5% of those treated with ICI <sup>[3]</sup>. Unlike most irAE which usually resolve within a few months, ir-IA can become chronic and persist even after ICI cessation, requiring long term immunosuppression <sup>[4]</sup>. The factors associated with chronic ir-IA and its significance regarding tumor outcomes remain largely unknown. With the increasing use of ICI in the adjuvant therapy, it is important to understand predictors and outcomes of chronic ir-IA in order to best counsel patients. <h3>Objectives</h3> To determine predictors and outcomes of chronic ir-IA in cancer patients exposed to ICI. <h3>Methods</h3> The CanRIO group, established since 2018, includes 9 academic sites in Canada and aims to describe the clinical presentation, management and outcomes of patients who developed rheumatic irAE (Rh-irAE) or those with pre-existing autoimmune diseases exposed to ICI using standardized data collection. The sites pooled data to develop a retrospective cohort of patients identified as having a Rh-irAE. We identified patients who developed ir-IA defined by new onset joint tenderness or synovitis in the absence of pre-existing rheumatic disease and who had at least 3 months of follow-up following ICI cessation. Chronic ir-IA was defined as having either persistent symptoms of ir-IA or the continued use of prednisone or DMARDs 3 months after ICI cessation. <h3>Results</h3> The CanRIO Retrospective Cohort included 193 ir-IA individuals of which 54 met our inclusion criteria. Forty-five of 54 (83%) had chronic ir-IA. Fifteen (33%) were female. Nineteen (42%) patients with chronic ir-IA had melanoma, 14 (31%) lung cancer and 8 (18%) genito-urinary cancer. Thirty-three (73%) were treated with anti PD-1/PD-L1, 14 (31%) with combination and none with anti-CTLA-4 only. Thirty-five (78%) were treated with conventional DMARDs and 1 (2%) with biologic DMARDs. Univariable logistic regression showed that ir-IA was more likely to become chronic in those with peripheral synovitis compared with those who did not have peripheral synovitis at presentation, (Table 1). Patients with chronic ir-IA had greater overall survival and progression-free survival compared to those with acute ir-IA (log rank tests, p&lt;0.01), (Figure 1). <h3>Conclusion</h3> A large proportion of ir-IA becomes chronic. The presence of synovitis at presentation is associated with arthritis persistence. Ir-IA is associated with improved overall survival and progression-free survival. <h3>References</h3> [1]Sharma, P., et al., Cancer Discov, 2021. [2]Roberts, J., et al., Autoimmun Rev, 2020. [3]Suarez-Almazor, M.E., et al., Support Care Cancer, 2020. [4]Braaten, T.J., et al., Ann Rheum Dis, 2020. <h3>Acknowledgements:</h3> NIL. <h3>Disclosure of Interests</h3> Alexandra Ladouceur: None declared, Lourdes Gonzalez Arreola: None declared, Shahin Jamal: None declared, Marie Hudson Consultant of: Boehringer Ingelheim. Grant/research support from: Bristol-Myers Squibb, Boehringer Ingelheim; Clinical studies: Astra-Zeneca, Janet Pope: None declared, Sabrina Hoa: None declared, Janet Roberts: None declared, David Moon: None declared, Ammana Karmali: None declared, Tatiana Nevskaya: None declared, Emma Schmidt: None declared, Nader Toban: None declared, Lindsay Cho: None declared, Thomas Barnetche: None declared, Carrie Ye: None declared.